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Written Assignment 3: Mass Relationships for Compounds

Answer all assigned questions and problems, and show all work.

1. How many atoms are there in 5.10 moles of sulfur (S)? (6 points)

(Reference: Chang 3.13)

2. How many moles of calcium (Ca) atoms are there in 77.4 g of Ca? (6 points)

(Reference: Chang 3.15)

3. What is the mass in grams of 1.00 × 1012 lead (Pb) atoms? (8 points)

(Reference: Chang 3.19)

4. Describe how you would determine the isotopic abundance of an element from its mass spectrum. (6 points)

(Reference: Chang 3.32)

5. Cinnamic alcohol is used mainly in perfumery, particularly in soaps and cosmetics. Its molecular formula is C9H10O.

1. Calculate the percent       composition by mass of C, H, and O in cinnamic alcohol. (8 points)
2. How many molecules of       cinnamic alcohol are contained in a sample of mass 0.469 g? (8 points)
3. How many carbon atoms are in 0.469 g of cinnamic alcohol? (8 points)

(Reference: Chang 3.41)

6. Allicin is the compound responsible for the characteristic smell of garlic. An analysis of the compound gives the following percent composition by mass: C: 44.4 percent; H: 6.21 percent; S: 39.5 percent; O: 9.86 percent. Calculate its empirical formula. What is its molecular formula given that its molar mass is about 486g? (20 points)

(Reference: Chang 3.43)

7. Tin(II) fluoride is often added to toothpaste as an ingredient to prevent tooth decay. What mass of fluoride in grams is in 258 g of toothpaste that has 15% tin (II) fluoride? (10 points)

8. What are the empirical formulas of the compounds with the following compositions?  (a) 2.1 percent H, 65.3 percent O, 32.6 percent S, (b) 20.2 percent Al, 79.8 percent Cl (20 points)

(Reference: Chang 3.49)

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